1. Field of the Invention
This invention relates to an electrosurgical instrument for permanently closing vessels in a human or animal, and more particularly to a bipolar electrosurgical instrument that seals vessels and vascular tissue by applying a combination of pressure and electrosurgical current.
2. Background of Related Art
A hemostat is commonly used in surgical procedures to grasp, dissect and clamp tissue. It is typically a simple pliers-like tool that uses mechanical action between its jaws to constrict vessels without cutting them. It is also typical for hemostats to have an interlocking ratchet between the handles so that the device can be clamped and locked in place.
Many hemostats are used in a typical open-surgical procedure. Once vascular tissue has been clamped with a hemostat, it is common for a surgeon to tie a suture around the tissue to close it off permanently prior to removing the hemostat. Several hemostats may be left in the surgical field until the surgeon has the opportunity to tie a suture around each section of clamped tissue.
Small blood vessels have been closed using electrosurgical instruments without the need for sutures. For example, neurosurgeons have used bipolar instruments to coagulate vessels in the brain that are smaller than two millimeters in diameter. These bipolar instruments are typically tweezers-like devices with two arms that can be deflected toward each other to grasp tissue. However, it has been found that these instruments are not capable of sealing blood vessels with diameters larger than about two millimeters. There has been a long-felt need for an easy way to seal larger vessels and vascular tissue bundles without the need for sutures.
It is thought that the process of coagulating small vessels is fundamentally different than vessel sealing. Coagulation is defined as a process of desiccating tissue wherein the tissue cells are ruptured and dried. Vessel sealing is defined as the process of liquefying the collagen in the tissue so that it crosslinks and reforms into a fused mass. Thus, coagulation of small vessels is sufficient to permanently close them. Larger vessels need to be sealed to assure permanent closure.
A number of bipolar electrosurgical forceps and clamps are known in the field. However, these instruments are not designed to apply the correct pressure to a blood vessel to achieve a lasting seal. All of these instruments also suffer from the drawback that they do not combine the simplicity and familiarity of a hemostat with a bipolar electrosurgical circuit.
An example of a bipolar electrosurgical power curve for vessel sealing is disclosed in a U.S. patent application entitled, xe2x80x9cEnergy Delivery System for Vessel Sealing,xe2x80x9d Ser. No. 08/530,495, filed Sep. 19, 1995, and is hereby incorporated by reference and made a part of this disclosure.
A U.S. patent application entitled, xe2x80x9cVascular Tissue Sealing Pressure Control and Method,xe2x80x9d Ser. No. 08/530,450, filed on Sep. 19, 1995, discloses another surgical tool for sealing vessels, and is hereby incorporated by reference and made a part of this disclosure.
U.S. Pat. No. 371,664 discloses a pair of electric forceps with positive and negative electric poles located on the jaws.
U.S. Pat. No. 728,883 discloses an electrothermic instrument in which electricity is used to heat one of the jaws of the instrument.
U.S. Pat. No. 1,586,645 discloses a bipolar instrument for coagulating tissue.
U.S. Pat. No. 2,002,594 discloses a bipolar laparoscopic instrument for treating tissue, whereby coagulation and cutting of tissue can be performed with the same instrument.
U.S. Pat. No. 2,176,479 discloses an instrument for finding and removing metal particles. The jaws of the instrument are designed to complete an electrical circuit when conductive material is placed therebetween. An insulated pivot and an insulated ratchet are used to prevent a short circuit.
U.S. Pat. No. 3,651,811 discloses a bipolar electrosurgical instrument for cutting and coagulating tissue.
U.S. Pat. No. 4,005,714 discloses bipolar coagulation forceps with jaws that open and close by way of an actuating sleeve.
U.S. Pat. Nos. 4,370,980 and 5,116,332 disclose an electrocautery hemostats wherein the hemostatic clamping function and the electrocautery function may be accomplished with a single instrument. Monopolar electrosurgical designs are shown and described.
U.S. Pat. No. 4,552,143 discloses a family of removable switch electrocautery instruments, including an electrocautery hemostat. Monopolar electrosurgical designs are shown and described.
U.S. Pat. No. 5,026,370 discloses an electrocautery forceps instrument having an enclosed electrical switching mechanism. Monopolar electrosurgical designs are shown and described.
U.S. Pat. No. 5,443,463 discloses coagulating forceps having a plurality of electrodes.
U.S. Pat. No. 5,484,436 discloses bipolar electrosurgical instruments for simultaneously cutting and coagulating tissue.
The article, xe2x80x9cThe Mechanism of Blood Vessel Closure by High Frequency Electrocoagulationxe2x80x9d discloses experiments upon the blood vessels of dogs. The sentence starting on the last line of page 823 describes xe2x80x9can electrode forceps, each of the blades being insulated form the other and each connected to a terminal of the high frequency generator.xe2x80x9d
The article, xe2x80x9cStudies on coagulation and development of an automatic computerized bipolar coagulatorxe2x80x9d discloses on page 150 that, xe2x80x9cIt was not possible to coagulate safely arteries with a diameter larger than 2 to 2.5 mm.xe2x80x9d On page 151, line 5, it is noted that xe2x80x9cVeins can be coagulated safely up to a diameter of 3 to 4 mm.xe2x80x9d
Russian Patent 401,367 discloses a bipolar instrument with a linkage that brings the working jaws together in a parallel manner.
Prior disclosures have not provided a design for a bipolar electrosurgical instrument capable of conveniently applying a constant pressure, from a calibrated spring-loaded source held by a ratchet, that is sufficient to seal vessels and vascular tissue.
It is the general objective of this invention to provide a bipolar electrosurgical instrument that can fuse tissue without the need for a suture or surgical clips. The instrument conducts electrosurgical current between two seal surfaces located on opposable jaws. The electrosurgical current passes through tissue clamped between the jaws and remolds the collagen to fuse the tissue and form a permanent seal.
One advantage of the invention is that blood vessels can be quickly fused and permanently sealed against passage of blood or other fluids. The instrument thereby reduces operating-room time, provides improved access to target tissues, and increases the efficiency of the surgical procedure.
Another advantage is that no sutures or staples are required to permanently seal blood vessels, and no foreign material is left in the body of the patient.
Yet another advantage is that vessels can be sealed as the instrument is applied, and then the instrument can be removed from the surgical field. This keeps the surgical field clear of extraneous tools that may hinder the surgeon""s access to the surgical site.
Yet another advantage is that the proper amount of pressure can be applied by the instrument to the vessel or vessels, thereby increasing the likelihood of a successful surgical outcome.
The bipolar electrosurgical instrument of the present invention comprises inner and outer members connected by an open lockbox, interlocking ratchet teeth, and electrical terminals with conductive pathways leading to seal surfaces. The inner and outer members each have a ring handle near a proximal end and an opposable seal surface near a distal end. The proximal end is held and controlled by the surgeon, while the distal end is used to manipulate tissue. The open lockbox joins the inner and outer members to allow arcuate motion of each opposable seal surface. The open lockbox is generally designed to provide lateral support so that both seal surfaces move in approximately the same plane. The seal surfaces are preferably aligned opposite each other when the instrument jaws are closed together. To provide lateral support, the open lockbox comprises a pivot and at least one flange extending over the inner member and attached to the outer member.
The instrument is tuned to provide a proper closure force by adjusting the dimensions of a shank portion on each of the inner and outer members. The shank portion is defined as the portion of each member bounded by its respective ratchet stub and the open lockbox. During use, the surgeon squeezes the ring handles to compress tissue between the seal surfaces. The shank portion of each member flexes in the manner of a cantilever spring, and can be locked in a deflected position with the ratchet to hold a constant force. It is one of the objects of the invention to provide a range of ratchet stops that correspond to a range of appropriate closure forces on the seal surfaces of the instrument.
Ratchet teeth are located on each member near the ring handle. The ratchet teeth are generally designed to interlock against the spring force from the shanks. The spring force is thus transmitted through the pivot to hold the seal surfaces against each other. A range of closure forces is required in an instrument, depending on the type and thickness of the tissue to be sealed. It is thus desirable to have several ratchet stops, each providing a progressively larger force to the seal surfaces.
An electrical connector is located on each ring handle. The electrical connector may be a metal post that is integrally formed with the member and ring handle. Bipolar electrical cables from an electrosurgical generator are connected to the instrument at the electrical connectors. An electrically conductive path on each of the inner and outer members conducts the electrosurgical current to the seal surfaces. The electrically conductive path may be along the stainless steel members. An electrically insulative coating is preferably bonded to the outer surfaces of the members to protect the surgeon and patient against inadvertent electrical burns.
The following terms are herein defined as follows. The applied force of the instrument is the total force being applied to the tissue between the jaws. The jaws are the members near the distal end of the instrument, from the lockbox to the tip of the instrument. The electrodes are the metal surfaces that conduct electricity to the tissue. The seal surface is the feature on the electrode that comes in direct contact with the tissue. The shank is the portion of each member between the lockbox and the ratchet. The ring handles are the elements on the members, near the proximal end of the instrument, that are grasped by the surgeon. The lockbox is the structure that allows the members to pivot, including the pivot pin and other cooperating surfaces. The inner member is the member that is generally captured in the interior of the lockbox. The outer member is the member that is on the outside of the lockbox. Electrode pressure is calculated by dividing the applied force over the complete area of the seal surface. Tissue pressure is calculated by dividing the applied force over the area of tissue placed between the jaws.
It has been found through experimentation that an instrument for vessel fusion (also referred herein as vessel sealing) should compress the tissue with a proper amount of pressure between the instrument jaws. The pressure is preferably sufficient to close any blood-carrying lumen. The pressure is preferably low enough so that the tissue is not split apart within the instrument jaws.
The jaws of the instrument should not short-circuit during the procedure. The tissue will typically decrease in thickness when electrosurgical current is applied, thereby allowing the seal surfaces to move closer together. This decrease in thickness should not result in the electrodes making direct contact with each other. Otherwise, a short circuit could give the electrosurgical current a preferential path around the tissue and may result in a poor seal.